When a permanent break occurs in one of the branches of a polling loop 2 wire cable, the devices which are affected are easily identified and enunciated by the security system control making it relatively simple for a service person to locate and repair the break. However, if a permanent short circuit or severe overload condition occurs on the polling loop, all of the devices on that loop can no longer communicate to the system""s control, rendering the security system inoperative. Locating and repairing a break in the polling loop is much simpler than locating and repairing shorts or overloads on the loop, especially when the short or overload manifests itself only when polling loop power and signals are applied to the loop.
Present commercial security systems which use an Ademco polling loop, advertised as Vplex, periodically test the loop to detect a short or overload condition as it may occur somewhere on the loop, but they cannot locate where the trouble condition exists. The control""s present reaction is to remove power from the loop and, after some time delay, re-apply power to the loop and re-test for the short or overload condition. The control has no course of action other than report the problem and continue to test the loop until the short or overload condition is removed by a service person.
To isolate the location of a short or overload condition on a polling loop requires significant time and effort even for skilled service personnel with suitable testing equipment. This is especially true in very large systems, in which many devices are distributed on the polling loop over several branches and thousands of feet of wire. In order to avoid this eventuality, some installers will xe2x80x9chome runxe2x80x9d all of the distributed sensors at a site to the inputs of all of their respective Vplex devices concentrated near the control""s panel. They do this to facilitate locating and repairing troubled wire run(s) to the sensors. This is an inefficient and costly way of employing the Vplex polling loop system.
In order to properly use the Vplex polling system without concern for shorts or overloads which may occur after installation or in the future, the installer must be given an effective means of locating a short or overload condition no matter where it may occur on the loop.
Some polling loop systems, such as that employed by Notifier, use relay-based, addressable short detection modules. They are designed to disconnect a shorted branch of the polling loop in order to keep the rest of the polling loop system operational. These modules are explained in the Notifier document, xe2x80x9cIntelligent Control Panel SLC Wiring Manualxe2x80x9d, dated Jul. 25, 2001, Rev C. Each module employs special relay-based short detection circuits and manually-operated rotary switches to identify the address of the affected module and, therefore, the location of the troubled branch or section of the loop. However, the manual does not explain how the proper module disconnects its associated branch on the loop since a short may manifest itself on every device and isolator module throughout the loop.
The Notifier module, which may be similar to other modules used in the Fire/Burglary Industry, requires special circuits, usually including the use of a relay, which must determine that its associated branch is the only branch that has the shorted condition. It must then disconnect its branch from the loop and simultaneously report its switch address to the control to identify the location of the troubled area of the loop.
Such circuits are likely to be expensive if they are to be accurate and dependable in making such a determination. In addition, the circuits must be immune to various disturbances on the loop to prevent unnecessary branch disconnects by any of the modules distributed on the loop.
The present invention provides a new Addressable Electronic Switch (AES) together with unique S/W (software) procedures for a system control to detect, locate, and isolate shorts, overloads, and other troubles, such as temporary breaks or disconnects, on a Vplex or similar 2-wire polling loop. It includes the use of unique inexpensive addressable electronic switches which are individually turned ON or OFF by the system control, to locate and isolate the troubled area on the loop. The addressable electronic switches are placed at strategic locations throughout the polling loop, and are individually commanded by the system control to either connect or disconnect its respective branch from the rest of the polling loop. In this way, the troubled area can be first located and then isolated from the rest of the polling loop.
The present invention provides an addressable electronic switch (AES) which can be applied to an Ademco Vplex or similar polling loop system. Although the following description of the invention relates to polling loop applications, such as Vplex polling loops, the present invention is equally applicable to any two-wire, DC-voltage powered, multi-branch, distribution system operating within its voltage and current limits. The present invention can be used in Class A fire polling loop applications wherein the detector circuit devices are connected in tandem in a return loop, or in Class B security polling loop systems wherein the detector circuits are connected in tandem or in parallel in branches that do not include return loops.